Jason Hollands, managing director of adviser Bestinvest, says: ‘The appeal of this rule change will be for experienced investors who like to research and take punts on individual shares.’

Another major worry is that small company shares tend to be less liquid. To turn them into cash you need to sell them – and that means finding a willing buyer.

For major stocks such as those in the FTSE 100 this is easy as there are millions of investors ready to stump up the cash. But far fewer people invest in small companies – and this could mean waiting for days while the share price ebbs away. The flip side is that some of the world’s most powerful companies started out as just a glimmer in an entrepreneur’s eye.

If you can sniff out the next McDonald’s or Apple, you could be sitting on a potential goldmine.

Alastair Thaw, head of investment at Barclays Stockbrokers, says: ‘The risks with small stocks are much higher – but so are the returns when you get it right.’

Mulberry is one of the most recognisable Aim-listed firms. With celebrities such as actress Sienna Miller and model Kate Moss sporting its handbags, its share price shot from 60p in May 2009 to 2472p in May last year.

Yet its shares crashed by a quarter in just one day on October 23 when it revealed drooping profits. Today they are worth 1250p.

Asos is another well-known Aim company that has boomed in the internet shopping revolution.

In October it reported profits had soared 40 per cent in a year to £44.4m. Its shares, which stood at just 100p in 2006, are now above 2600p.

But for every success there are just as many failures.

Shares in Aim-listed Madagascar Oil were suspended in 2010 when the African island’s government tried to take away its licence to explore.

A far safer way to tap into the rapid growth of small businesses is through a fund that invests in hundreds of different companies. Over the past 12 months, the average UK small company fund has risen 23 per cent, turning £10,000 into £12,300, according to data analyst Morningstar.

Had you invested £10,000 in the best-performing funds over the past three years – Cazenove UK Smaller Companies and Fidelity UK Smaller Companies – you would now be sitting on more than £18,100.

Mr Hollands says: ‘The hope is that funds investing in smaller companies get in very early, at a good price, just as the company is about to grow. It’s all about boosting your capital – not income.’